Submitted by Renata Cristina Julio da Silva (rcj.julio@hotmail.com) on 2018-04-11T17:50:35Z No. of bitstreams: 1 Dissertação.pdf: 2389871 bytes, checksum: 5ee2a84bc455331f9e1b35a12bed3205 (MD5) / Approved for entry into archive by Elza Mitiko Sato null (elzasato@ibilce.unesp.br) on 2018-04-11T18:35:14Z (GMT) No. of bitstreams: 1 silva_rcj_me_sjrp.pdf: 2389871 bytes, checksum: 5ee2a84bc455331f9e1b35a12bed3205 (MD5) / Made available in DSpace on 2018-04-11T18:35:14Z (GMT). No. of bitstreams: 1 silva_rcj_me_sjrp.pdf: 2389871 bytes, checksum: 5ee2a84bc455331f9e1b35a12bed3205 (MD5) Previous issue date: 2018-03-16 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / O processamento da cana-de-açúcar para a produção do etanol e do açúcar vem crescendo a cada ano no Brasil, gerando grandes quantidades de subprodutos de biomassa, a destacar a vinhaça e o bagaço de cana. O principal uso dessas biomassas é na geração de energia (bagaço de cana) e na fertirrigação (vinhaça). Porém a busca por novas alternativas de utilização do bagaço de cana e da vinhaça são necessárias na tentativa de agregar ainda mais valor a estes subprodutos. Sendo assim, estes subprodutos podem ser utilizados no processo de carbonização hidrotérmica (CHT), uma técnica capaz de converter termicamente a biomassa úmida em um material sólido rico em carbono, denominado carvão hidrotérmico. Devido às características físico-químicas do carvão hidrotérmico, diversas aplicações têm sido sugeridas, sendo umas delas o uso como possível fertilizante. No processo de CHT, também é gerada uma fração líquida denominada água de processo. Conhecer a composição orgânica do carvão hidrotérmico e da água de processo é fundamental para entender os efeitos do uso do carvão hidrotérmico como um fertilizante e para propor um destino adequado para a água de processo. Neste contexto, o presente trabalho teve como objetivo fazer um screening inicial dos principais compostos orgânicos presentes no carvão hidrotérmico e na água de processo, utilizando um espectrômetro de massas com ionização por electrospray (ESI-MS), seguido da identificação dos compostos orgânicos não voláteis, utilizando cromatografia em fase gasosa acoplada à espectrometria de massas (GC-MS). A partir dos resultados obtidos com a análise por ESI-MS pode-se concluir que as condições de preparo do carvão hidrotérmico e da água de processo, como temperatura e acidez, influenciam na composição orgânica destas amostras. As principais classes de compostos observados apresentaram estruturas semelhantes a proteínas, lipídeos, compostos fenólicos e compostos nitrogenados. Na análise dos extratos de carvão hidrotérmico obtidos por GC-MS foram identificados principalmente compostos derivados de benzeno, compostos cíclicos, compostos fenólicos e ácidos graxos. Já nas amostras de água de processo os principais compostos identificados foram compostos fenólicos, ácidos carboxílicos e compostos nitrogenados. / The processing of sugarcane for ethanol and sugar production has been growing every year in Brazil, generating large quantities of biomass by-products, including vinasse and sugarcane bagasse. The main use of these biomasses is for energy generation (sugarcane bagasse) and fertigation (vinasse). However the search for new alternatives of sugarcane bagasse and vinasse uses are necessary in an attempt to add even more value to these byproducts. Thus, these by-products can be used in the hydrothermal carbonization (HTC) process, a technique capable to convert thermally the wet biomass into a solid carbon-rich material called hydrochar. Due to the physical-chemical characteristics of the hydrochar, several applications have been suggested, one of them being the use as a possible fertilizer. In the HTC process, a liquid fraction called process water is also generated. Knowing the organic composition of hydrochar and process water is fundamental to understand the effects of the use of hydrochar as a fertilizer and to propose a suitable destination for process water. In this context, the present work aimed to perform an initial screening of the main organic compounds present in hydrochar and process water using an electrospray ionization mass spectrometer (ESI-MS), followed by the identification of the non-volatile organic compounds, using gas chromatography coupled to mass spectrometry (GC-MS). From the results obtained by ESI-MS analysis, it can be concluded that the conditions of production for hydrochar and process water, such as temperature and acidity, influence the organic composition of these samples. The main classes of compounds observed showed similar structures proteins, lipids, phenolic compounds and nitrogen compounds. In the analysis of hydrochar extracts obtained by GC-MS, benzene derivatives, phenolic compounds and fatty acids were identified. In the process water samples, the main compounds identified were phenolic compounds, carboxylic acids, and nitrogen compounds.

Hydrothermal carbonization (HTC) is a process where elevated temperature and pressure is used in order to convert biomass to hydrochar, a coal-like substance with good dewatering properties and many potential uses. HTC can be used to treat digestate from anaerobic digestion, but the process water that remains after the hydrochar has been recovered needs to be treated further in the wastewater treatment plant. In order to make HTC more competitive compared to other sludge treatments it is important to find a good use for the process water. The main objective of this master thesis was to investigate the effects of recirculating HTC process water to the anaerobic digestion. To achieve the objective, both theoretical calculations and experimental trials were performed. The experimental trials were conducted with an Automatic Methane Potential Test System (AMPTS II) in order to investigate the anaerobic digestion in laboratory scale. In the first trial, three substrates, process water, hydrochar, and primary sludge were tested for their biochemical methane potential (BMP). All substrates were mixed with inoculum. Process water had a BMP of 335 ± 10 % NmL/gvs (normalized CH4 production in mL per g added VS (volatile solids)), hydrochar had BMP of 150 ± 5 % NmL/gvs, and primary sludge had a BMP of 343 ± 2 % NmL/gvs. The methane production was almost the same for process water as for primary sludge i.e. no inhibitory effects could be seen when process water was mixed with only inoculum. In the second trial, a more realistic scenario was tested where process water was co-digested with primary sludge at different ratios. The results from the second trial were not statistically reliable and therefore cannot be used on their own to determine with certainty if the process water could have an inhibitory effect in a full-scale anaerobic digester. However, the combined results from both trials indicate that it is unlikely that the process water would have an inhibitory effect. The possible increase in methane yield, if the digestate from a biogas facility was treated in full-scale implementation of the HTC process, was calculated theoretically. The produced process water would have the capacity to increase the methane production with approximately 10 % for a biogas facility. For the calculations, the BMP for process water was assumed to be 335 NmL/gvs and no synergetic effects was considered.

No description available.

Befolkningsökningen och därmed efterfrågan på energikällor som tillhandahålls från fossila bränslen leder till allvarliga miljöproblem på grund av utsläpp av växthusgaser. En annan utmaning är att effektivt hantera organisk avfall som till exempel matavfall som genereras världen över. Matproduktionen orsakar stora miljöproblem som övergödning, klimatpåverkan, kemikaliespridning, regnskogsavverkning och utfiskning. Det är därför viktigt att matsvinnet minskar men också att effektiva metoder används för hantering av avfallet för att inte belasta miljön ytterligare.  En lösning för att hantera organiskt avfall, och samtidigt producera en förnybar energikälla är att använda anaerob rötning för att producera biogas. Vid anaerob rötning bryts organiskt material ner i en syrefri miljö, vilket resulterar i produktion av biogas som innehåller koldioxid och energirik metangas. Biprodukten som bildas är rötrest, som kan vidare användas som gödsel.  Den anaeroba rötningsprocessen har olika utmaningar där biogasprocessen kan stabiliseras och effektiviseras genom tillsats av hydrokol. Hydrokol är ett kolrikt material framställd från hydrotermisk karbonisering av biomassa. Eftersom det finns mycket begränsad forskning på kontinuerlig anaerob rötning av matavfall med tillsats av hydrokol, och ingen forskning har utförts på hydrokol som är tillverkat från skogsindustriellt avfall, så var det viktigt och av intresse att genomföra denna studie.  Syftet med studien är att undersöka hur tillsats av hydrokol påverkar biogasproduktion, metanproduktion och stabiliteten i en kontinuerlig anaerob rötningsprocess. Vidare syftar studien till att analysera effekterna av hydrokol på rötresterna som genereras, undersöka möjligheterna av sammankoppling av en befintlig rötkammare med en HTC reaktor, samt bedöma om det är ekonomiskt försvarbart att investera i hydrokol som additiv i rötningsprocessen. Målet har varit att undersöka om tillsats av hydrokol ger högre biogasutbyte, ökad metanproduktion och en stabil rötningsprocess. Målet har även varit att analysera rötresterna, utföra en materialflödesanalys över när Karlskogas rötkammare sammankopplas med en HTC reaktor, samt utföra en livscykelkostnadsanalys för att svara på om det är ekonomiskt försvarbart att investera i en HTC anläggning, alternativt att köpa in hydrokol externt.  De laborativa försöket gjordes på Karlstads universitet där rötningen var en enstegs anaerob samrötning som gjordes i två kontinuerligt matade reaktorer. Inmatning och uttag av gas gjordes en gång om dagen där försöksserierna pågick under 68 dagars tid. Substratblandningarna eftersträvades efterlikna substratförhållandena på Biogasbolaget i Karlskoga. Inmatat material, det vill säga substratblandningen utgjorde 8,5% av ensilage, 0,6% av glycerol, och 90,9% av substrat (matavfall och flytgödsel). Detta förhållande är detsamma som på Biogasbolaget. I en av reaktorerna användes substratblandningen och i den andra substratblandningen och hydrokol. Hydrokolet blandades in med substratblandningen vid en koncentration på 8g/l. Materialflödesanalysen gjordes över Karlskogas biogasanläggning där flödena ritades ut i programmet Stan 2.5. LCC gjordes utifrån två olika scenarion, om hydrokol köps in externt alternativt att en HTC-reaktor ansluts till biogasanläggningen. Det valdes att beräkna utifrån scenarion om metanutbytet ökar med 17%, enligt resultat från studien gjord av Maria Kristoffersson eller om utbytet ökar med 53% enligt resultat från den här studien.  Resultatet visar att tillsats av hydrokol som additiv ger en ökning på 59% för biogas utbytet och 53,5% för metanutbytet. I medelvärde från rötningsdag 27 till 68 så resulterade biogasproduktionen för hydrokolsreaktorn i 533 ml/g VS. Medelvärdet för referensreaktorn resulterade i 70 ml/g VS. Det här resulterar i en procentuell ökning med 663%. Eftersom misstankar finns att referensreaktorn inte bildar biogas som den ska har biogasproduktionen jämförts med tidigare studie som har gjorts på ungefär samma substratblandning och samma utrustning. Biogasproduktionen i medelvärde för referensreaktorn för (Leijen, 2016) resulterade i 335 ml/g VS. Procentuella skillnaden i biogasproduktion resulterar då i 59% mellan referensreaktorn och hydrokolsreaktorn. Metanproduktionen i hydrokolsreaktorn resulterade i medelvärde till 367 ml/g VS, i referensreaktorn till 18 ml/g VS och i referensreaktorn i Leijens studie till 237 ml/g VS. Jämfört med Leijens resultat resulterade den procentuella ökningen i metangasproduktion till 53,5%. En stabil rötningsprocess bekräftades genom att pH på rötresterna resulterade i 7,66 under hela rötningsprocessen.  Det är möjligt att sammankoppla Karlskogas befintliga anläggning med en HTC-anläggning och återföra rötresterna för hydrokolsproduktion. Rötresterna med ett högre kol-och näringsinnehåll kan återanvändas och recirkuleras för produktion av hydrokol. Av 10 tonTS/dag rötrester som kommer ut från rötningskammaren kommer 2,46 tonTS/dag att recirkuleras för hydrokolsproduktion. Resten av rötresterna kan användas vidare som gödsel.  Det är ekonomiskt försvarbart att investera i hydrokol som additiv till rötningsprocessen. Genom att bygga en HTC-anläggning, där tillsatsen av hydrokol kan ge 17% respektive 53% högre metanproduktion resulterar nettovinsten i 363 miljoner respektive 1237 miljoner kr över en 20-årsperiod. Alternativet är att köpa in hydrokol externt, där nettovinsten uppgår till 177 miljoner respektive 1052 miljoner kr över samma tidsperiod. Livscykelkostnadsanalysen visar att det är ekonomiskt mer fördelaktigt att investera i en HTC-anläggning jämfört med att köpa hydrokol externt. / The population growth and thus the demand for energy sources provided by fossil fuels leads to serious environmental problems due to greenhouse gas emissions. Another challenge is to effectively manage organic waste such as food waste generated worldwide. Food production causes major environmental problems such as eutrophication, climate impact, chemical dispersion, rainforest deforestation and depletion. It is therefore important that food waste is reduced, but also that effective methods are used to manage the waste so as not to burden the environment further.  One solution for managing organic waste, while producing a renewable energy source, is to use anaerobic digestion to produce biogas. In anaerobic digestion, organic material is broken down in an oxygen-free environment, resulting in the production of biogas containing carbon dioxide and energy-rich methane gas. The by-product formed is digestate, which can be further used as fertilizer.  The anaerobic digestion process has various challenges, where the biogas process can be stabilized and made more efficient by adding hydrochar. Hydrochar is a carbon-rich material produced from hydrothermal carbonization of biomass. Since there is very limited research on continuous anaerobic digestion of food waste with the addition of hydrochar, and no research has been conducted on hydrochar produced from forest industry biosludge, it was important and of interest to conduct this study.  The aim of the study is to investigate how the addition of hydrochar affects biogas production, methane production and the stability of a continuous anaerobic digestion process. Furthermore, the study aims to analyze the effects of hydrochar on the digestate generated, investigate the possibilities of connecting an existing digester with an HTC reactor, and assess whether it is economically justifiable to invest in hydrochar as an additive in the digestion process. The goal has been to investigate whether the addition of hydrochar provides higher biogas yield, increased methane production and a stable digestion process. The goal has also been to analyze the digestate, perform a material flow analysis of when Karlskoga's digester is connected to an HTC reactor, and perform a life cycle cost analysis to answer whether it is economically justifiable to invest in an HTC plant, or to purchase hydrochar externally.  The laboratory experiments were carried out at Karlstad University where the digestion was a single-stage anaerobic co-digestion in two continuously fed reactors. Gas was fed and withdrawn once a day and the experimental series lasted for 68 days. The substrate mixtures sought to mimic the substrate conditions at Biogasbolaget in Karlskoga. Input material, i.e. the substrate mixture consisted of 8.5% silage, 0.6% glycerol, and 90.9% substrate (food waste and liquid manure). This ratio is the same as at Biogasbolaget. One of the reactors used the substrate mixture and the other used the substrate mixture and hydrochar. The hydrochar was mixed with the substrate mixture at a concentration of 8g/l. The material flow analysis was made over Karlskoga's biogas plant where the flows were drawn in the program Stan 2.5. LCC was made based on two different scenarios, if hydrochar is purchased externally or if an HTC reactor is connected to the biogas plant. It was chosen to calculate based on scenarios if the methane yield increases by 17%, according to results from the study made by Maria Kristoffersson or if the yield increases by 53% according to results from this study.  The results show that adding hydrochar as an additive gives an increase of 59% for the biogas yield and 53.5% for the methane yield. In average from digestion day 27 to 68, the biogas production for the hydrochar reactor resulted in 533 ml/g VS. The average value for the reference reactor resulted in 70 ml/g VS. This results in a percentage increase of 663%. Since there are suspicions that the reference reactor does not produce biogas as it should, the biogas production has been compared with previous studies that have been done on approximately the same substrate mixture and the same equipment. The biogas production in average for the reference reactor for (Leijen, 2016) resulted in 335 ml/g VS. The percentage difference in biogas production then results in 59% between the reference reactor and the hydrochar reactor. The methane production in the hydrochar reactor resulted on average to 367 ml/g VS, in the reference reactor to 18 ml/g VS and in the reference reactor in Leijen's study to 237 ml/g VS. Compared to Leijen's results, the percentage increase in methane gas production resulted in 53.5%. A stable digestion process was confirmed by the fact that the pH of the digestate resulted in 7.66 during the whole digestion process.  It is possible to interconnect the existing Karlskoga plant with an HTC plant and recycle the digestate for hydrochar production. The digestate with a higher carbon and nutrient content can be reused and recycled for hydrochar production. Out of 10 tonTS/day of digestate coming out of the digestion chamber, 2.46 tonTS/day will be recycled for hydrochar production. The rest of the digestate can be further used as fertilizer.  It is economically justifiable to invest in hydrochar as an additive to the digestion process. By building a HTC plant, where the addition of hydrochar can provide 17% and 53% higher methane production, the net profit results in 363 million and 1237 million SEK over a 20-year period. The alternative is to purchase hydrochar externally, where the net benefit amounts to SEK 177 million and 1052 million respectively over the same time period. The life cycle cost analysis shows that it is economically more advantageous to invest in an HTC plant compared to buying hydrochar externally.

Anaerob rötning är en naturlig nedbrytningsprocess av organiskt material som tar tillvara på avfall samtidigt som nyttig energi kan utvinnas. På Biogasbolaget AB i Karlskoga omvandlas substrat som matavfall, gödsel och ensilage till biogas som sedan kan uppgraderas till fordonsgas. Fordonsgasen kan användas som drivmedel till bussar i närområdet. Det bildas dessutom en rötrest som används som biogödsel, men som är kostsam för företaget. Rötkamrarna i Karlskoga är överdimensionerade i förhållande till den mängden substrat som levereras, vilket innebär att de kan ta hand om mer gas än det som bildas i dagsläget. Tidigare studier har visat att tillsats av hydrokol kan öka metangasproduktionen. Därför var syftet med studien att utvärdera ifall hydrokol kan öka metangasproduktionen i satsvis anaerob rötning. Målen var att jämföra två olika hydrokol; skogsindustriellt och kommunalt, samt att komma fram till en optimal dos. Eftersom området är relativt nytt var det också av intresse att ta reda på hur klimatpåverkan förändras vid tillsats av hydrokol genom att utföra en enkel livscykelanalys.   Utvärderingen av hydrokolets potential i anaerob rötning utfördes genom satsvis rötning i två omgångar. Substrat och ymp hämtades från Karlskogas biogasanläggning. De doserna hydrokol som testades i båda försöken var 4, 8 och 10 g/l samt referensfallet 0 g/l vilket motsvarade Karlskogas förhållanden. Det gjordes även försök med endast hydrokol för att ta reda på om det var hydrokolet i sig som producerade metangas. Den satsvisa rötningen visade att det kommunala hydrokolet med en dos på 8 g/l gav mest metangas (841 Nml/g VS) jämfört med referensen 0 g/l (435 Nml/g VS) vilket var en ökning med 93%. Det skogsindustriella hydrokolet med en dos på 8 g/l visade en ökning med 16,6% (517 Nml/g VS) jämfört med referensen 0 g/l (443 Nml/g VS). Den enkla livscykelanalysen visade att det resulterade i en större minskning av utsläpp när dieselbussar kan bytas ut mot hydrokolsbaserad biogas jämfört med vanlig biogas. Vid tillsats av kommunalt hydrokol till biogasprocessen blev besparingen 14783 ton CO2.ekv./år vid utbyte av diesel och för skogsindustriellt hydrokol motsvarade besparingen 8938 ton CO2.ekv./år. Det jämfört med biogas som produceras utan hydrokol som vid utbyte av diesel sparar 7688 ton CO2.ekv./år. Massflödesanalysen visade att det teoretiskt är möjligt att använda Karlskogas rötrest för att använda som substrat till HTC-anläggningen och därmed införa ett cirkulärt system. Däremot visade metallanalysen att det finns risk för förhöjda mängder tungmetall i rötresten, vilket skulle kunna leda till att de inte klarar de krav som finns för att certifiera biogödseln.   För Biogasbolaget AB i Karlskoga innebär resultaten att de med 8 g/l kommunalt alternativt skogsindustriellt hydrokol skulle kunna öka sin metangasproduktion med 93% respektive 16,6%. Däremot kan det leda till problem med metallhalterna i rötresten som riskerar att överstiga gränsvärdena som finns för biogödsel. / Anaerobic digestion is a natural decomposition process of organic material that utilizes waste while extracting useful energy. At Biogasbolaget AB in Karlskoga, substrates such as food waste, manure, and silage are converted into biogas, which can then be upgraded to vehicle fuel. The vehicle gas can be used as fuel for buses in the local area. Additionally, a digestate is formed, which is used as biofertilizer but is costly for the company. The digesters in Karlskoga are oversized compared to the amount of substrate delivered, which means they can handle more gas than is currently being produced. Previous studies have shown that the addition of hydrochar can increase methane gas production. Therefore, the aim of the study was to evaluate whether hydrochar can increase methane gas production in batch anaerobic digestion. The goals were to compare two different types of hydrochar: from the forestry industry and municipal sources, and to determine the optimal dosage. Since the area is relatively new, it was also of interest to determine how the climate impact changes with the addition of hydrochar by conducting a simple life cycle analysis.   The evaluation of hydrochar's potential in anaerobic digestion was carried out through batch digestion in two rounds. Substrate and inoculum were obtained from Karlskoga's biogas plant. The doses of hydrochar tested in both experiments were 4, 8, and 10 g/l, as well as the reference case of 0 g/l, which corresponded to Karlskoga's conditions. Experiments were also conducted with hydrochar alone to determine if it was the hydrochar itself that produced methane gas. The batch digestion showed that the municipal hydrochar with a dosage of 8 g/l produced the most methane gas (841 Nml/g VS) compared to the reference of 0 g/l (435 Nml/g VS), which was an increase of 93%. The forestry industry hydrochar with a dosage of 8 g/l showed an increase of 16,6% (517 Nml/g VS) compared to the reference of 0 g/l (443 Nml/g VS). The simple life cycle analysis showed that it resulted in a greater reduction in emissions when diesel buses can be replaced by hydrochar-based biogas compared to regular biogas. When municipal hydrochar was added to the biogas process, the savings amounted to 14,783 tons of CO2 equivalent per year through diesel substitution. For forest industry hydrochar the equivalent resulted in savings of 8,938 tons of CO2 equivalent per year. This is in comparison to biogas produced without hydrochar, which saves 7,688 tons of CO2 equivalent per year when substituting diesel. The mass flow analysis showed that it is theoretically possible to use Karlskoga's digestate as substrate for the HTC plant, thus introducing a circular system. However, the metal analysis revealed a potential risk of elevated levels of heavy metals in the digestate, which could prevent it from meeting the requirements for certifying the biofertilizer.   For Biogasbolaget AB in Karlskoga, the results mean that with 8 g/l of municipal or forest industry hydrochar, they could increase their methane gas production by 93% and 16.6%, respectively. However, this could lead to issues with metal levels in the digestate, which may exceed the threshold values set for  biofertilizer.

Many environmental crises are threatening to collapse human societies, but also life on the Earth as we may know. Climate change due to anthropogenic global emissions is one of the main issues, but also soil degradation, and the management of the enormous amount of organic wastes that are harmfully released into the environment by human activities. On the one hand, direct spreading of biowastes onto the land is often limited due to eutrophication or pollution by toxic compounds. On the other hands, these biomasses may contain nutrients, such as phosphorus (listed as a critical raw material) and nitrogen, which could be recovered to sustain the high demand in expensive soil amendments and fertilizers. Thus, finding new solution to close the loop towards circular economy and sustainable processes is crucial, nowadays, to convert the global trends and restore the delicate equilibrium in the water-food-energy nexus, with soil ‘under special surveillance’. In this framework, many researchers are focusing their attention on hydrothermal carbonization (HTC) as a possible candidate, in particular to treat moist biowastes and obtain useful solid (hydrochar) and liquid (HTC liquor) products. Nutrients contained in biowastes are sensitive to HTC process parameters and initial feedstock properties, thus it is crucial to analyze their distribution and (im)mobilization among the HTC products for their reuse in soil. On the other hand, since some organic compounds are generated during the thermochemical process, which may be responsible for toxicity to plants and other organisms, analysis of their possible toxicity towards the biosphere becomes crucial before implementation at a large scale. This thesis collects our efforts to explore new processes and deepen the knowledge about the possibility to produce amendments suitable for soil application from hydrochar. The core is from a process engineering perspective, focusing on the production phase and the characterization of the products, never forgetting any possible limits or the implications on ecotoxicological issues. In the first part of the thesis, ‘How to make hydrochar a soil amendment?’ is the main question. Based on few pioneer studies about composting of hydrochar, we assessed a complete analysis of hydrochar co-compost, produced from the 25-day aerobic stabilization of digestate of organic fraction of municipal solid waste, together with a fraction of its hydrochar, and green waste. Under the umbrella of C2Land project (funded by The European Institute of Innovation & Technology -EIT), we produced this new amendment in specifically designed bioreactors, then we characterized the products from the point of view of physico-chemical properties, nutrients distribution, toxicity to plants and mammalian cells. We are confident that the crucial result of toxicity removal from hydrochar through composting will attract the interest of many stakeholders, since implementing HTC in anaerobic/aerobic plants is almost ready to be applied at a large scale. Moreover, an experimental campaign performed at the University of Leeds further explored the effect of some other post-treatments on hydrochar composition and phytotoxicity, depending on the initial feedstocks (manure, sewage digestate, water hyacinth, and grass). The second part of the thesis was dedicated to nutrients recovery, necessary when some harmful matrixes - such as the municipal sewage sludge digestate - are not allowed to be reused for agricultural purposes, due to law limitations or pollution issues. In this case, nutrients recovery (N, P) could be achieved chemically, via HTC and struvite precipitation, being struvite recognized as a good fertilizer. Firstly, we performed a techno-economic assessment of the implementation at a district level of HTC-centered sewage sludge management. The mass reduction of waste streams may have some important effects on transportation costs, while the recirculation of HTC liquor back to the anaerobic digestors can imply more biomethane production with increased revenues. A mass balance for the potential of N and P recovery through struvite precipitation in the centralized facility was also assessed. Secondly, a near-zero waste treatment process for municipal sewage sludge via HTC was designed according to the available literature and preliminarily analyzed at lab level. The fractionation of the different types of phosphorus was analyzed through the STM-P protocol before and after HTC, confirming the mineralization of organic phosphorus during the process. Citric acid was validated as a good green solvent for phosphorus extraction and high-quality struvite precipitation, even if the process was not still optimized in terms of yields. Future works may identify the best process parameters for final metal recovery from liquid byproducts in order to internally recirculate them back to water line, and to characterize the leached hydrochar as purified renewable fuel or soil amendment. Thus, the proof-of-concept chain would be confirmed and could be applied to the sustainable HTC-centered biorefineries of the future.